The Optical Absorption Edge of p-Type Tl_(1-x)GaPr_xSe₂and TlGaSe₂

Abstract

p-TlGaSe 2 and Tl (1-x) , GaPr x Se 2 single crystals were grown by the modi¢ed Bridgman-Stockbarger method. The absorption measurements were carried out in p-TlGaSe 2 and TI (1-x) GaPr x Se 2 samples in temperature range 10^320 K with a step of 10 K. The phonon energies calculated for p-TlGaSe 2 , p-TI 0.999 GaPr 0.001 Se 2 and p-Tl 0.995 GaPr 0.005 Se 2 are 34.0 meV, 30.0 meV and 35.0 meV, respectively. At 300 K, the direct band gaps of p-TlGaSe 2 , p-Tl 0.999 GaPr 0.001 Se 2 and p-Tl 0.995 GaPr 0.005 Se 2 are 2.165 eV, 2.164 eVand 2.155 eV and the indirect band gaps are 2.110 eV, 2.122 eV and 2.128 eV, respectively. There is an abrupt change in the direct energy peak for p-TlGaSe 2 in the temperature ranges 230-250 K, for p-Tl 0.999 GaPr 0.001 Se 2 and p-Tl 0.995 GaPr 0.005 Se 2 in the temperature ranges 195-215 K. On the other hand, indirect energy peaks for p-Tl 0.999 GaPr 0.001 Se 2 and Tl 0.995 GaPr 0.005 Se 2 are in the temperature ranges 215-235 K.

Urbach tail and optical characterization of gadolinium-doped TlGaSe2single crystals

“…In conclusion, our results agree with those of the literature [5,9,17,[23][24][25][26][27][28][29]. TlGaSe 2 and TlGaSe 2 : Gd single crystals were grown by the Stockbarger method.…”

“…The temperature coefficients (δ) of the direct band gap were calculated to be 5.185 × 10 −4 eV K −1 for both samples by fitting the experimental curves using equation (6). A reasonably good agreement was obtained with results of [23,24]. Also, for TlGaSe 2 and TlGaSe 2 : Gd samples β were calculated to be 185 K. For indirect band gap, the temperature coefficient was calculated by using the same method, to be 3.599 × 10 −4 eV K −1 , and β was found to be 205 K for TlGaSe 2 sample.…”

Optical and Photoelectric Properties of TlInS2 Layered Single Crystals

“…The direct energy gap and the width of the tail of TlInS 2 layered single crystal are listed in Table (2). These results are in agreement with literature reports [6,22,24].…”

Modification of the optical and elastic properties of TlGaSe2 layered semiconductor produced by the memory effect

“…The experiments were carried out under nitrogen atmosphere. While the sample was heated from ∼80 to ∼300 K using a heating rate of 1 K min 1 controlled by temperature controller (Lake Shore Model 336), the pulses were recorded by PXI 5124 High Resolution Digitizer. By employing the method of pulse-echo overlap, ultrasonic sound velocity was calculated versus temperature.…”

“…TlGaSe 2 is a typical ternary A B C III III VI 2 dichalcogenide belonging to the family of van der Waals bonded layered semiconductors in a bulk phase. TlGaSe 2 is a p -type semiconductor having a high optical transmission (∼70%) at the UV -visible wavelengths and a direct energy band gap ranging between about E g ∼ 2.0 and ∼2.23 eV [1][2][3][4]. Some researchers have reported that TlGaSe 2 is a typical indirect band gap semiconductor with a band gap varying from ∼1.83 to ∼2.13 eV [5][6][7][8] at ambient conditions.…”